2. LED provides almost mono chromatics light. This suitable for small distance transmission. It is infact, a low cost device as compared to diode lasers.
Line Communication
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Transmission lines are used to interconnect points separated from each other. For example interconnection between a transmitter and a receiver or a transmitter and antenna or an antenna and a receiver are achieved through transmission lines. Line communication may be in the form of electrical signal or optical signal.
Optical Fibres
An optical fibre is a long thread consisting of a central core of glass or plastic of uniform refractive index. It is surrounded by a cladding of material of refractive index less than that of the core and a protective Jacket of insulating material.
There are three types of optical fibre configuration
1. Single mode step index fibre 2. Multi mode step index fibre 3. Multi mode graded index fibre.
Applications of Optical Fibres
1. A bundle of optical fibres is called light pipe. This pipe can transmit as image. Since the pipe is flexible, it can be twisted in any desired manner. Hence it is used medical and optical examination of even the inaccessible parts of human body, e. g., in endoscopy.
2. Optical fibres are used in transmission and reception of electrical signals by converting them first into light signals.